1. Field of the Invention
The present invention relates to a digital audio tape drive, and more particularly to a rotary head digital audio tape drive having a plurality of read/write heads.
2. Description of Related Technology
Magnetic tape storage devices are widely used for bulk storage because the magnetic tape reliably stores data and is relatively inexpensive. Digital audio tape (DAT) is a type of magnetic tape which stores data in a digital format. It is a popular medium for backing up higher speed persistent storage devices such as hard disks and floppy disks. The stored data may be of any type including, for example, programs, audio, images, motion pictures, and electronic documents.
DAT drive systems typically use a rotary-head format, originally developed for video cassette recorders (VCRs), to read and write data. The rotary-head format is also referred to as a helical scan format since the read/write heads spin diagonally across the tape. FIG. 1a shows a schematic diagram of a rotating drum 101 for a DAT drive. The drum has a pair of read heads 103, 105 and a pair of write heads 107, 109 alternately arranged on the circumference of the rotating drum 101. While the DAT drive is reading or writing digital data from or onto the tape 111 which is being passed around the drum 101, the drum 101 itself rotates. Thus, when the DAT drive reads data from the tape 111, the read heads 103, 105 alternate in sensing the tape 111. The same alternation applies for writing with the write heads.
The alternate contribution of the read and write heads 103, 105, 107, 109 in reading and writing tracks 113 is illustrated in FIG. 1b. If the track N is written by the write head A 107, then tracks N+2n (where n is an integer) are written by the same head, write head A 107, and tracks N+2n+1 (where n is an integer) are written by the other head, write head B 109, respectively. Likewise, if the track N is read by the read head A 103, then tracks N+2n (where n is an integer) are read by the same head, read head A 103, and tracks N+2n+1 (where n is an integer) are read by the other head, read head B 105.
While the DAT drive is performing a read or write process, the digital data is transformed into electric current. In the writing process, the digital data is converted to an electric current signal which makes the write head 107, 109 generate a magnetic field to magnetize the tape 111. The write head 107, 109 must generate a sufficiently strong magnetic field so that the surface of the tape retains magnetization strong enough for the read head to read, but not so strong as to interfere when an adjacent track is read. In turn, to generate the appropriately strong magnetic field, a proportional electric current (write current) must be supplied to the write heads 107, 109. In the reading process, on the other hand, to correctly transform the analog electrical signal generated from sensing the magnetization of the tape to digital (binary) data requires appropriate equalization. The equalization generally includes filtering and amplifying the electrical signal. In filtering the signal, an appropriate cut-off frequency must be used to remove noise, which usually has higher frequencies than the signal representing the digital data, without affecting the ability to regenerate the stored data. Also, an appropriate boosting value must be supplied to ascertain the shape or levels of the signal.
The write current which allows appropriate magnetization, i.e., not too strong or too weak magnetization, depends on the design and manufacture characteristics of the write heads 107, 109. The parameters such as cut-off frequency and boosting value depend on the read heads 103, 105 generating the signal to be equalized. Because a plurality of read heads 103, 105 or write heads 107, 109 are alternately used in a DAT drive, each having unique characteristics, the driving and equalization circuit must operate for each head. In this regard, statistically averaged parameters have been used for designing circuitry receiving and transmitting signals to a rotating drum having a plurality of heads. However, because every average parameter is applied to all heads having inevitably different electromagnetic properties, this may generate errors which decrease the reliability of read and write operations. Further, heads which have electrical response parameters far beyond the average value cause too many errors to be usable. Thus, when an error prone head is tested at the factory it must be disposed of and replaced.
There is, thus, a need to improve the reliability of read and write operation of a DAT drive having a plurality of read and write heads.
Furthermore, there is a need to make use of heads which have a parameter beyond the average range in a DAT drive having a plurality of read and write heads.
The aforementioned needs are satisfied by several aspects of the present invention.
One aspect of the present invention provides a magnetic tape dive, comprising: a plurality of read heads capable of scanning a magnetic tape and produce a first electrical signal representing magnetization of the magnetic tape; a plurality of write heads capable of magnetizing a magnetic tape in accordance with a second electrical signal provided thereto, a drum having a circumference around which the read and write heads are alternately mounted, wherein the drum rotates while the magnetic tape drive is performing a read or write operation; a plurality of first memory circuits each one of which stores a parameter for each one of the plurality of read heads; a first modifying circuit capable of modifying first electrical signal by using the read head parameters stored in the plurality of the first memory circuits; a plurality of second memory circuits each one of which stores a parameter for each one of the plurality of write heads; a second modifying circuit capable of modifying the second electrical signal by using the write head parameters stored in the plurality of second memory circuits; and an activation circuit capable of selectively activating the plurality of first and second memory circuits to provide the parameters stored therein to either of the first or second modifying circuits.
Another aspect of the present invention also provides a method for processing an electrical signal to be magnetized onto a magnetic tape with a plurality of write heads, comprising the steps of: storing a head parameter of each of the plurality of write heads; processing an electrical signal by selectively using the head parameters; magnetizing the magnetic tape with a plurality of write heads according to the processed electrical signal, wherein a specific head are used when the electrical signal processed by using the parameter of the head is magnetized.
Still another aspect of the present invention provides a method of processing an electrical signal for magnetizing a magnetic tape with one of a plurality of write heads, comprising: storing a head parameter for each of the plurality of write heads; processing an electrical signal by using at least one of the head parameters; magnetizing the magnetic tape by feeding the processed signal to one of the plurality of write heads.
Still further aspect of the present invention provides a method of processing electrical signals read from or written to a magnetic tape, comprising: providing a plurality of read heads adapted to scan a magnetic tape and produce a first electrical signal representing magnetization of the magnetic tape; providing a plurality of write heads adapted to magnetize a magnetic tape in accordance with a second electrical signal provided thereto, providing a drum having a circumference, wherein the drum rotates while the magnetic tape drive is performing a read or write operation; configuring the plurality of read and write heads to be alternately mounted around the circumference of the drum; providing a plurality of first memory circuits each one of which stores a parameter for each one of the plurality of read heads; providing a first modifying circuit for modifying the first electrical signal by using the read head parameters stored in the plurality of first memory circuits; providing a plurality of second memory circuits each one of which stores a parameter for each one of the plurality of write heads; providing a second modifying circuit for modifying the second electrical signal by using the write head parameters stored in the plurality of second memory circuits; and providing an activation circuit for selectively activating the plurality of the first and second memory circuits to provide the parameters stored therein to either of the first or second modifying circuits.
These and other features of the present invention will become more fully apparent from the following description and claims.